Albert Barnes' Notes on the Whole Bible - Ezra 7:12
The title, “king of kings,” is assumed by almost all the persian monarchs in their inscriptions.Perfect peace - “Peace” is not in the original, and the word translated “perfect” occurs only in this place. Some prefer to take it as an adjective descriptive of Ezra (see margin); others (Septuagint) as the opening word of the first paragraph of the letter, and give it the meaning, “it is completed.” read more
The Pulpit Commentary - Ezra 7:12
Artaxerxes, king of kings . "King of kings, kkshayathiya khshaya-thiyanam ," an equivalent of the modern shahinshah , was a recognised title of the Persian monarchs, and is found in every Persian inscription of any considerable length. It was a title that had been used occasionally, though not at all frequently, by the Assyrian monarchs, and naturally expressed the fact that those monarchs for the most part maintained the native princes on the thrones of the countries which they... read more